The Nerf Vulcan requires 6 D type batteries to operate. Since these are hard to come by and are quite expensive (even more so if rechargable) I came up with a mod to use 3 18650 type Li-On rechargable batteries that can be picked up on Ebay pretty cheaply. They might run out of juice a little sooner than the D cells, but are fast to charge.

I designed this mod especially so that it doesn't require any modification of the original battery compartment. The 3 Li-On cells provide a little higher voltage/more power than the 6 D cells (11 vs 9V) but IMHO not so much more that it should damage the motor. However, use this at your own risk (I take no responsibility).

To make this easy printable, I chose to not use supports but glue the different parts together with acetone. However, I have included full designs for those that want to try to print it in one go.

Also, it is necessary to make an electrical connection using soldering iron. For the bottom I used a round-cut part of a tin can and the top is a nail, both connected by a wire. This is visible on the photos.

The supports are not necessary, but provide extra support so the whole contraption stays in place.